Pit-type furnace



July 11, 1950 J. M- GUTHRIE' PIT-TYPE FURNACE 2 Sheets-Sheet 1 Filed 001;. 8, 1946 l I I r I I l l l l ll l I r l I l l I I l II J. M. GUTHRIE PIT-TYPE FURNACE July 11, 1950 Filed cat. a, 1946 2 Sheets-Sheet 2 wooooo ooooomw 00000 Patented July 11,1950

ticularly pit-type furnaces forheating-crew];-

to forging, rolling; or -rtl'iefilikeranti-the invention efficient and more uniformhe'ating" of ingots--or other articles .may'be obtained.

"pit," designed with side-walls which are Irelatiyely uniformly spacedwithi espect to averti'cal center i"line"a'rising from the "centeriof'qtl'iet hearthpf the Ditfflnd; .thusvcoriStituted, is'adapted to" the iiiill consists in certainnewand usefukimprovem'ents'5floor *plansiami practice of a great many steel in h structure hf aceawhfeby'more mil1s.'"1However;insomecases; Ihave'foundit preferable" .to provide pits: of {relatively narrow ielon'gatefform; asyiewed. in planfandun such elongate-pits; I provide, 3.5"disl2ingifish6di from a i My inventionrelatesto pitfliype furnacesgeparing :ingots' 10f steel orother";imeta1;i-" preparatory Theart is familiar with a furnace" known-as the center fired :pit.:" -Asdtsnamesu gests? theqo'fthe structure of "my;said.gcopending applieation,

j against the cover of thepit'and spradsyumbrella fu'mbiella instrea=ms7- spaced fadially sfoutward charge supported cm the" pit bottom around the :1 a':burnei-fcenti-al1y"in' eachz'endtwall" of thepit. These burners are" 11'00aljd10li the longitudinal verticalmid planeof theipitytheburnei s dixte'ct their flames into a-combixstiom5 spacefiprovid ed burner opening. Thestream offiamesfimpinges'i'15-between-the tops" of the ingotsinharged in;.th e"pit "and the co ver'of the.:pit, and the burnersxare so angled: inwtheir position thattheffiame; projected from" the-"centrally located burners *arefspread 1: an'gulaily' "substantially; to cove'r the-- horizontal hearth, and" tlie *bui'ning fcolumnof fuel"streams vertically upward-between the ingots of the like, over the'ch'arge; 'andgthen the flames and hot products; of combustion "descent?from "the from the burning 'e'olumn "sustainedbythemen 20*expanse" of fisaideombustiori. chamber; in furthertral burner: "Uponapproaehing'wthe bottoni of the pit the, streams"of'hotwa;ste"-gase find"'egress N :ancef of; theflatter effect the opposite sidettwa-lls, andf'sometimesithe opposite end'rwalls too, are "*foutwardlybowed as viewed" in-p1an;: this "contourside walls and communicate? withi'heat exchan e means that arei'efiective"to"salvage-*iarge quan-m25. 'a: swirling findsprezding of-the flames-delivered tities of :residual' heat tfronf-the "gasesrtanw-to transferthe heat 6th" the ieom'biistion air "which is fed to the burner."' Whi1e"many* -advantages have been recognized" in 'the" use"of*-*the" center- I fired pit; several disadvantages are to be notedi- -ao "each end rw'all'are a 'rang d-- t a a For example, the arrangement ofithe burneryin the center of the "pit floorfrresultsin arrediiction in the ingot capacityof'a *pifipfigiverisiz; -the capacity of a pit-being in gener'al' proportional -"an'gularly:into:the combustion: space above the "ingots'f: In eachof'the end walls'iof'thepit outlet yportsmre"provided-"immediately" above, the coke breeze jo'n the hearth; "and' thesegoutlet ports-{in "longitudinal; vertical mid -plane" of" the ipit chamberfwhereby 'exact 'symm'etnyexists between the burners and outlet "p'ort's each wall "and "*betweerr' the':burners"'and oiitbiiilt'"portsin the to receive ingots? Consequentlyy' imfirder-to obtain a specified pit capacity, itrhas been necessary to-build a larger-and more costly pit than would he thecase if the entii "-burner in serviceifails 'to funotiomproperlyi the i it may be noted that the impingemeniipf a stream of burning *fuel against the pit*e0ver=i's del'eteri0us ottom available for the suppor -ingots.- I

to the cover struet-ur Fui thermorepwhemthe entire pit inu'st be' shut' down' ,it being understod fi ure 1.

2 that it is not =uncommofii for burners to' re'quire Referring to =thefidrawing's "the pit furnacemay attention over prolonged periods 'ef service. e eonstructed a's afiinit'having 'ZSihflflhitfbl In an application foi -Unite&" States'-fietters "'"it'may'have aabattery ofpits; 'a-s indieate'd' by the reference numeral Zfi'riFigure 1.""Th'e" pits :trated and deseribedy an ingot pit type furnace which eliminates the 'obje'ctions-to -the-=ieenteri fired pit, While obtaining or rtaining its more -important advantagesi 'ihe pit" o'f r myEsaid prior iii-application is? as in thewease of" the eentei ii'ied i viewed' =in plan? but" theirperiphe'ral wane 3*, 3

and 4-; '4maybe"internallyeurifed' outwardliwto increase the durability, :and *stnrdiness" ofrt'con- "'=st ri-iction',*-and to promote more 'effeetivamoven ent (ifibuininfuel and productwofeoinbusabove the ingots.

other side of said center line;

The hearth or bottom 8 of the pit includes one or more cleanout openings 9, which are normally filled with the coke breeze 10, or other suitable material which provides the floor upon which the ingots H stand, as shown inFigure 2. 'I he may be arranged in each wall 3 to give this desired effect, I advantageously provide two outlet ports for each burner, such ports being arranged substantially directly below the associate burner, one on each side of the longitudinal vertical midplane of the chamber.

The effect of the described burner and outgo port, organization is to. insure at all customary IZQ llCSYOff'fiI'lIlgfLfa, uniform distribution of heat throughout the pit chamber and its charge. The

.; .burners l3 are luminous flame burners, and, as

the art well knows, a luminous flame burner is one whose flame contains unburned particles or ,molecules offuel In the travel of the fuel from pit is provided with a cover l2 that istemporarily 3 removable to permit the ingots to be charged into the pit and removedfiIt will be observed that the entire area of the bottom of the pit is, available for the support of ingots, with the ingots arrangedand spaced properly in accordance with ingotsize and shape.

The pit chamber,,it willbe seen,'is of greater depth than the heighth of the ingots supported on the hearth '8, providing a combustionspace between thetops of the ingots and the cover l2.

Each pit is provided. with a particularly elfective organization of burners, together with an effective arrangement of waste gasports for removing the hot "waste gases 'or products of combustio'nfrom the pit chamber, all to the end that a more effective" distribution of heating effect 'may be established andmaintained throughout ,fallportions of the pit chamber, not only when the pit is fired at'a" maximum heating capacity I but also when the burners are turned down for soaking or hQIding 'the' charge of ingots.

More particularly, Ifprovide a burner. I 3 in each :of the opposite end walls of the pit chamber. These burners I3 are aligned with the longitudinal center line of the chamber, and are located' to direct burning columns of fuel and air into the combustion space above the ingots inthe chamber. The burners may be canted upwardly, as appears in Figure 2, to give, a lift to the burning. columns entering the combustion space It is important to note the burners are inclined or extend angularly, as viewed in a horizontal plane above the pit, and

by virtue of this burner arrangement the burning column delivered by one burner into the combustion space above the ingots is directed angularly to one side of the longitudinal center line of the chamber, while the column delivered by the opposite burner is directed angularly to the The two columns, thusentering the combustion space in substantial parallelism, spread and :provide an exceedingly effective coverage of the horizontal expanse of, the pit chamber, and it maybe noted, that the outwardly curved internal surfaces of. the

.. chamber walls cooperate with the angled columns of flames and hot gases to provide the desired coverage and uniform heat distribution in the pit chamber. Y

Below the burners, outlet ports 14 open through the end walls 3, v3 and lead into heat-exchange units l5 for preheatingthe combustion air that is fed through a duct system 16 to the burners. The arrangement of the outlet ports is such that r the drafting ofv waste gases from immediately above the bottom of the pit chamber is substan- .ti'ally symmetrical with respect to the firing effect of theburners abov'e the ports. While a single wide outlet port,or row of three or more ports,

the ,burner these particles are progressively heated to incandescence and burned, so that the heat release of the flame is distributed over a long path of flame travel, rather than being con- ,centrated at a point located a relatively short interval from the burner. Accordingly, my arrangementof angled long luminous flames in a combu'stionfspac'e above the tops of the ingots does not' 'mean that combustion is completed .jabovethe tops of the ingots. On the contrary,

burning tongues 'of flame are drawn downward betweenthe ingots as well as between the ingots and the pit, walls, such' movement of the flames being promotedby the pressure created by the injected burning fuel and air at the top of the pit, plus the suction of the draft acting through I the symmetrically arranged outlet ports. A bene- .ficial prolongation and distribution of combustion, and a thoroughly disseminated movement of the hot waste gases, are provided in the pit at allcustomary firing rates.

The waste gases emerging from the outlet ports i l enter. recuperators 55 at the opposite ends of the pit structure. Various types of recuperators may be adapted for the purpose of salvaging heat from the waste products of combustion within the pit, and imparting a high degree of preheat to the air for the combustion of fuel. However,

I prefer recuperators of the construction illustrated and described in my copending application, Serial No. 581,626, filed March 8, 1945, and

it-is needless toan understanding of my present invention to consider in detail the structure of suoh recuperatorsh Suffice it herein to say that the waste gases' are delivered from the outlet ports [4 through the recuperators to a stack or other vent, while the. air for combustion is led through v the recuperators and ducts IE to the burners 13.

The preheated air delivered by ducts IE to the burnersis subject to the control of valves 28.

The fuel is delivered to the burners through nozzles 29, each of which includes a control valve,

- and, by the adjustment of such fuel valves and the air control valves, the desired rate of combustion may be established in each pit chamber.

It goes without saying that conventional proportioning mechanism for air-fuel ratio control, and for temperature and pressure control in each pit chamber may be provided.

Within the terms of the appended claims certain variations and modifications of the structure I described may be practiced without departing fromthe spirit of the invention.

I claim as my invention:

1-.In a Dit-typeingot furnace of general rectangularform inlplan, having refractory side and end walls, a hearth for supporting ingots on end, ;a movable cover, means for firing the furnace including.v piping for fuel and combustion air,

a flue system for leading the hot products of combustion fromv the furnace, and heat-exchange and toward one of said side walls and the burning column delivered by the other burner is directed upwardly and toward the other side wali, said columns expanding laterally to provide a turbulent body of flames and hot gases distributed over the horizontal expanse of said combustion chamber above the ingots in the furnace, and outlet ports opening through the furnace walls into said flue system at points located near i said hearth, said ports being substantially symmetrical with respect to said burners as viewed in plan and being productive of a distributed flow of the flames of hot gases downwardly from said combustion chamber and over and around the bodies of the ingots in said furnace.

2. In a pit-type ingot furnace of general rectangular form in plan, having refractory side and end walls, a hearth for supporting ingots on end, a movable cover, two burners for delivering burning columns of fuel and air into the furnace, piping for delivering fuel and combustion air to said burners, a flue system for leading the hot products of combustion from the furnace, and

- heat-exchange means arranged with said flue sidewalls of said furnace being outwardly bowed.

as viewed in plan, said burners being angled relatively to said side walls, whereby the burning column delivered by one burner is directed toward one of said outwardly bowed side walls and the column delivered by the other burner is directed toward the other said side wall, said columns expanding laterally to provide a turbulent body of flames and hot gases distributed over the horizontal expanse of said combustion chamber above the ingots in the furnace, and outlet ports opening through the furnace walls into said flue system at points located near said hearth, said ports being substantially symmetrical with respect to said burners as viewed in plan and being productive of a distributed flow of the flames of hot gases downwardly from said combustion chamber and over and around the bodies of the ingots in said furnace.

3. In a pit-type ingot furnace of general rectangular form in plan, having refractory side and end walls, a hearth for supporting ingots on end, a movable cover, two burners for delivering burn ing columns of fuel and air into the furnace, piping for delivering fuel and combustion air to said burners, a flue system for leading the hot products of combustion from the furnace, and heat-exchange means arranged with said flue system for preheating said combustion air; the improvements herein described wherein said furnace includes a combustion chamber extending between the tops of said ingots and said cover, said two burners opening severally through the end walls of said furnace at points substantially midway between the furnace side walls, said burners being angled relatively to said side walls and inclined upwardly, whereby the burning column delivered by one burner is directed upwardly and toward one of said side walls and the column delivered by the other burner is directed upwardly and toward the other side wall, said columns expanding laterally to provide a turbulent body of flames and hot gases distributed over the horizontal expanse of said combustion chamber above the ingots in the furnace, and outlet ports opening through the furnace walls into said flue system at points located near said hearth, said ports being substantially symmetrical with respect to said burners as viewed in plan and being productive of a distributed flow of the flames of hot gases downwardly from said combustion chamber and over and around the bodies of the ingots in said furnace.

, JAMES M. GUTHRIE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,867,221 Hepburn July 12, 1932 2,126,095 Dean Aug. 9, 1938 FOREIGN PATENTS Number Country Date 527,765 Great Britain Oct. 16, 1940 OTHER REFERENCES Soaking Pits Fired Simultaneously from Two Sides, Blast Furnace and Steel Plant, Sept. 1937, pages 995,996, 997. 

